As organizations grow and expand geographically, they desire their telecommunications systems to operate as a single, geographically dispersed, switching system with full feature transparency. U.S. Pat. No. 4,488,004 discloses providing such capability in a network of PBXs by equipping the PBXs with data controllers and transmitting feature-related data messages between individual PBXs' data controllers over data links that interconnect the PBXs in the network. This unfortunately requires that the PBXs be interconnected by a data network of the data links, in addition to the usual communications-carrying tie trunks. Furthermore, the data network follows a proprietary protocol, and therefore is not suited for being implemented via existing, open or public, data networks. U.S. Pat. No. 5,093,827 discloses providing the desired capability by interconnecting the PBXs via a proprietary center stage network (CSN). Since the CSN is proprietary, this unfortunately does not facilitate implementing of the desired capability via existing, open or public, networks. And U.S. Pat. No. 5,182,750 discloses a switching system architecture for interconnecting remote switching nodes to a central controller via standard ISDN links set up through intervening switching systems or the public switching network. It uses the same protocol to communicate between the switching nodes and the central controller as is used by the switching systems or switching network. Therefore, it also does not facilitate implementation of a feature-transparent distributed switching system that uses a proprietary protocol via an open or public network.